Is the U.S. becoming a nation of home renters?

A still-struggling economy, coupled with the ongoing effects of the housing mortgage crisis that helped spark the Great Recession, have left many Americans unwilling or unable to purchase a home.

According to U.S. census data quoted by RealtyTrac, the number of renters in American homes rose to 34.5 percent in 2011, with close to one-fourth of all U.S. metro regions seeing higher rental rates.

Then there's the rise of the Millennials, new workers ages 18 to 34, who are foregoing purchasing homes -- at least for now -- in favor of renting. And that demand, according to Mortgage News Daily, has helped pushed the construction of rental units to a 25-year high.

But it has also created dog-eat-dog situations for would-be renters in many big U.S. cities,

"Applying for an apartment is just as competitive as applying for a job," Tom Gatta, a 27-year-old living in a 600-square-foot, one-bedroom apartment in San Francisco with his wife, said in a report released last month by the California Economic Summit.

And San Francisco, according to a new survey by the home rental search site Zumper.com, is currently the most expensive U.S. city for renters.

Zumper says the median rent for a one-bedroom apartment in San Francisco last month came in at $3,100 - beating out New York, another city known for its astronomic rental costs.

But the study notes New York City still has the dubious distinction of having a higher median price per bedroom for its rental apartments -- as well as the top three most expensive neighborhoods for rentals in the U.S. (For the record, those neighborhoods are Tribeca, DUMBO and the Flatiron District).

Detroit, currently struggling to emerge from bankruptcy, is at the bottom of the Zumper list with the cheapest rents in a major U.S. city -- with one bedroom apartments there costing, on average, $565 per month.

For the record, here's Zumper's list of the most expensive big cities for rentals, along with the medium monthly price of renting a one-bedroom.